Sno Scoot Has Me Stumped

Backwoods M Max

Backwoods M Max

New member
Joined
Mar 31, 2011
Messages
1,052
Location
New England
The sno scoot that my father in law picked up for my son a few years ago really has me stumped. 2 Winters ago when it came home we managed to get it running and rode it around a little. It was after that and this winter with my son being almost 2 we tried to get it going. I had bought a bunch of parts from freedom cycle to tune it up and now it's running but I'm really at a loss.

We changed all the gas line and put a proper in tank filter in it. It had a wire screen clunk and external filter before. The hose had rotted off at the grommet for the gas line inside the tank. I cleaned the carb took it down as far as a could and gave it a nice bath in chem dip. The main jet seemed fine, the pilot jet was very gunked up and the idle air screw was at 2 3/4 turns. I was able to get the idle jet and main jet out but the nozzle is stuck. someone already tried to get it out and ground off the slot with a bad screwdriver tip so it's stuck for good. I sandblasted and cleaned up the spark plug and ran it for a little while and it started doing what it did before, spitting gas out the muffler. In the past someone tightened the idle needle so much it tried to extrude the tip through the seat so I didn't know what was going on and I just cleaned the carb again. I took it all down, gave it another chem dip bath and put it back together. Float heigh is 15mm (basically parallel to the bowl seat when you flip it upside down). That's just with the weight of the float against the spring plunger in the needle. Is that wrong? The needle/seat set look good no groove in it but maybe it needs changing anyways. Is there a viton needle tip available for these things? I went through the carb and got all the belt dust out of there and rebuilt the primary with new rollers.

I started it up and checked the idle rpm with the inductive pickup on my multi meter and it was around 2250 with the screw set to max idle speed. I'm running the air idle screw at 1/2 turn since the tip is so thin now from being over tightened. I could feel the clutch grabbing just around 4000 on the meter so that's right. I jumped on it and zipped down the driveway. It didn't want to accelerate at first and at the other end it wanted to die unless I would keep blipping the throttle. i came back and pulled the plug and it was jet black after 5 minutes of running. I'm really at a loss with this thing. I'll pull compression tomorrow just to see what it is, I haven't pulled the reeds yet to look at them. It's kind of in limbo as to who's it really is. It was bought for my son but with the intention of it staying at his house most of the time. I do most of the wrenching though so ultimately I see myself doing the work on it.
 
checked compression. kicked 150psi on 5 kicks, 90 psi on first kick. When I pulled the plug you could smell the gas in it. Chase a needle and seat or main/idle jets?

Maybe I'm checking the float height wrong? I flipped the carb over so the float is closing the needle and it's parallel but it's not fully compressing the spring/plunger that's inside the needle. At float set height should it be pushing against the needle solid? Is the float buoyant enough to fully compress that plunger when closing the needle? If that's the case, the setting is WAY off.
 
Hello
If you don´t have a service manual you can download it here for free, https://www.pdf-archive.com/2011/08/03/sno-scoot-manual/
Chapter 5-6 is about the carb and it says:
The float arm should be resting on the needlevalve, but not compressing the needle valve.
Float height: 14,6- 16,6mm (0.57- 0.65 in)
On snoscoot.com you have a carb rebuild kit. Look at the pic there and you see two rubbercaps that are important for the snoscoot/snosport.
Are yours still there?

Andreas
 
Well it sounds like the float is in spec. I've been talking with Aaron at snoscoot.com and he seems to think that it might be an enlarged pilot. When I bought the fuel line and clutch rollers I only got the carb plugs and bowl oring because I wanted to see what I had when I got into it. I guess I should have bought the full kit and changed everything. At this point I'm thinking it's either the enlarged pilot like Aaron thinks or the needle/seat is leaking by. I have the choke cable adjusted all the way down so I know there is slack in the choke cable but it might not actually be seating. The plunger rubber is in good shape though so if it seats that shouldn't be a problem.
 
OK
Follow his advice and try that before you do anything else.
I hope you can get it to work alright. These are fun machines. My 8 yrs old daughter have a snosport and it´s much more fun know when she
can keep up with the speed when we are out driving.
Andreas
 
I'd like to get it worked out without too much more fuss. I don't really want to buy a carb they are EXPENSIVE hopefully new guys will fix it. My son is just turning 2 so he's a ways from riding it himself but I would love to give him rides on it. I'm hoping that new guts will fix it. When we first got it running there was a big air bubble between the pump and carb that took a while to clear which had me thinking the needle wasn't leaking by. It might turn into one of those "sum of the parts" repairs.
 
Your last post answered the one question i had, it has a fuel pump and NOT gravity fed. There is a good chance that the fuel pump can "push" fuel past the needle and seat assembly causing the over rich condition.
 
Yup they have a little diaphragm pump like you would see on a tractor or larger lawn mower. Oil injection is fixed too no variable rate. There is a t and the pump just squirts oil into the fuel on its way to the fuel pump. My prime suspect is needle/seat. The carb looked so neglected I doubt it has a different pilot jet unless it has been there forever.
 
It does. It's a genuine Yamaha plug. This is an early carb with a brass plug in the other side. I'm leaning towards needle/seat leak by next. Possibly the choke leaking by but the plunger has good rubber on the bottom and there is plenty of free play in the choke cable.
 
also pull the baffle out of the pipe just to be sure its not plugged up from oil---to check this even further pull the whole muffler assembly off of the exhaust---I always thought our scoot ran better with out the baffle---not saying this will fix it, i'm sure you have a carb issue, this will just eliminate a possible plugged exhaust while you get it dialed in
 
Tod said:
pretty sure its just a single screw---sounds way better without it too
Click to expand...

I will have to pull it out when I get home next week. I also have a new needle and seat and a pilot jet. I'm changing those then if it still floods out I'm looking at the choke plunger not seating. I don't really see it being the choke I have more than the specified 1-3mm of free play on the choke lever after it's been dropped flat so I know it's closing.
 
I just don't know where else to go with this thing. I pulled the carb apart and changed the pilot jet as well as the needle and seat. I set the float very conservatively. Unless it needs to be 100% closed at level not just putting pressure against the spring plunger. The engine is still dumping a mixture of black gas/oil out the exhaust. The choke plunger is still all there and the bottom rubber has a nice indentation on it so it's bottoming out. I just can't figure out how this much gas is getting into the motor and it's still running. Can the oil pump drive seal fail and just dump straight oil back into the motor?
 
Missing oil pump parts

A couple of bucks said:
Mabey were looking the wrong direction. Does it have STRONG spark?
Click to expand...

Very strong. Enough to keep it firing with a spark plug dripping wet. I just took a look at the oil pump and the parts diagram and found the adjuster mech completely missing. I would have to guess its just dumping oil past the seal into the motor from that end.

FullSizeRender 4.jpgFullSizeRender 5.jpg
 
You must log in or register to reply here.


Back
Top